Lichens have been studied as bioindicators of air quality for more than 100 years. A terrific presentation called Urban Lichens: Environmental Indicators from NC State researchers dives deep into worldwide studies of lichens as bioindicators of pollutants.

More recently, researchers are finding that when toxic emissions are under control in urban areas, other factors affecting lichen abundance and diversity come into play, like temperature and humidity level. What is the urban heat island-lichen interplay? The theory: lichen abundance and diversity on urban trees can be an indicator of the level of urban heat island effect but also an indicator of the success of urban heat island mitigation efforts, like tree planting. More research is underway.

In this fascinating article, Council member and horticulturist Laura Wyeth explores the truly enthralling biology of lichens—simultaneously vulnerable and cannily adaptive organisms. —Michelle Sutton, Ed.

Some topics really hold up … with nearly 1400 views, this was the top viewed blog post in 2017–even though it originally appeared in 2015! Former NYC Director of Street Tree Planting Matt Stephens and NYSUFCEditor Michelle Sutton coauthored this story questioning commonly held beliefs about “fall hazards,” mostly as it applies to B&B trees, but they also discuss the interaction of the fall season with other production methods, like bare root. Nina Bassuk helped craft the section called “The Five Branches of Transplanting Success,” which will be of interest to anyone planting trees.

Council member and horticulturist Laura Wyeth, with Japanese knotweed. Photo by Larry Decker

Japanese knotweed (Polygonum cuspidatum; Latin synonym Fallopia japonica) is indisputably a major nuisance in the urban forest. NYC Parks Natural Resources Group has documented extensive research and control methods they’ve used, in partnership with the Bronx River Alliance and other entities, to combat knotweed along the Bronx River and in other natural areas in the City’s five boroughs.

Regardless of what combination of chemical and mechanical means are employed, control of Japanese knotweed is widely acknowledged to be imperfect at best. While we can and should manage its presence in our urban forests, this plant is here to stay.

Why and how is Japanese knotweed so successful at colonizing the most degraded sites? Why is it so hard to control? And what are some of the positive attributes of the plant that you might not hear much about? In this piece, Council member Laura Wyeth, a horticulturist with a particular interest in weed science, explores some of what makes Japanese knotweed unique.

Laura Wyeth:

Japanese knotweed is a plant caught up in the polarization of our times. Both its virtues and its malevolence have been inflated in the public imagination, and it is at once known as both miracle drug and botanical monster. In Canada, a nation not prone to paranoia, it has been described as “a demon weed so relentless, bloody-minded and destructive, it’s been called the terrorist of the plant kingdom.” Strong words for a creature with no teeth, claws, or toxicity to humans. Internet herbalists tout its miracle cancer-fighting properties with equal hyperbole. Yet with this plant, the quiet facts are more interesting than the hype.

Mission

New York State’s Urban Forestry program is a partnership of public, private and volunteer organizations and individuals that fosters comprehensive planning, management and education throughout New York to create a healthy urban and community forest and enhance quality of life.